For resin molded articles to be used in automobile interiors and exteriors, building interior materials, household electric appliances and so on, and resin molded articles to be used in organic glass that is used as an alternative material for inorganic glass, etc., techniques for laminating a decorative sheet for the purpose of surface protection and impartment of design property are used. Decorative sheets to be used in these techniques can be classified broadly into lamination-type decorative sheets and transfer-type decorative sheets. In the lamination-type decorative sheet, a surface protective layer is laminated on a support base material so as to be situated on the outermost surface, and a molded resin is laminated on the support base material side, so that the support base material is incorporated in a resin molded article. On the other hand, in the transfer-type decorative sheet, a surface protective layer is laminated on a support base material directly or with a release layer interposed therebetween, the release layer being provided as necessary, and a molded resin is laminated on a side opposite to the support base material, followed by separating the support base material, so that the support base material does not remain in a resin molded article. These two types of decorative sheets are used properly according to the shapes of resin molded articles and required functions.
In recent years, resin molded articles obtained using a transfer-type decorative sheet have been required to have more advanced design property with diversification of users' preferences, and for example, an advanced design having a deep and glossy vivid hue like one obtained by applying a deep-colored lacquer, such a design with raven blackness, has been desired. Not only a decorative layer but also a base material or a surface protective layer contributes to display of a hue having a color and gloss like raven blackness. In this connection, a method has been proposed in which by using a specific pigment in a decorative layer and enhancing the transparency of a layer disposed on the outermost side of a resin molded article, for example, such a deep color that images of surroundings are projected on a surface of the resin molded article is displayed (see, for example, Patent Document 1).
The technique described in Patent Document 1 is a technique relating to a lamination-type decorative sheet in which a decorative layer is in contact with a base material disposed on the outermost side of a resin molded article. On the other hand, in a transfer-type decorative sheet, a surface protective layer, a support base material and so on are formed outside a decorative layer, and thus in a sheet state, the decorative layer is not exposed. The transfer-type decorative sheet is integrated with a molded resin, and the surface protective layer exposed after separation of the support base material forms a surface of the resin molded article. Accordingly, when a transfer-type decorative sheet is used, it is further difficult to ensure that a color and gloss in observation of a resin molded article decorated by a decorative sheet is made close to a desired color and gloss set in design of a product.
For solving the above-mentioned problem, for example, Patent Document 2 discloses a decorative film including a base material, a release layer, a surface protective layer, a primer layer and a decorative layer in this order, wherein the surface protective layer is composed of a cured product of an ionizing radiation curable resin composition, the primer layer is composed of a primer layer forming resin composition containing a polymer polyol, an isocyanate-based curing agent, and a binder resin having a glass transition temperature Tg of 77° C. or lower, and the content of the binder resin is 10 to 60% by mass based on the total amount of the polymer polyol and the binder resin.